Acceptable Noise Level in Children with Unilateral Cochlear Implant and Bimodal Hearing

Background and Aim: Difficulty in perception of speech in noise is one of the main complaints of hearing-impaired people. Due to profound hearing loss in cochlear implant (CI) users, they need higher signal-to-noise ratio for a better perception. Bimodal fitting is a preferred way  for CI users because it prevents auditory nerve degeneration, is a complement of frequency range at the opposite ear, an is less invasive to provide binaural hearing. Acceptable noise level (ANL), as a reliable test to assess noise tolerance, has not yet been used in comparing children with bimodal hearing and CI. This study aimed to determine whether bimodal fitting can help CI children tolerate more noise. Methods: This descriptive-analytical study was conducted on 13 children with unilateral CI and bimodal hearing. Audiometry test was performed at aided and non-aided conditions. Then, their noise tolerance was assessed by the Persian version of ANL test. Results: Bimodal hearing resulted in  statistically significant increase in ANL. The  mean of ANL at unilateral CI and bimodal hearing conditions were 6.15±2.90 and 4.77±1.70, respectively. Conclusion: Bimodal fitting lead to more noise tolerance in unilateral CI children due to the combination of binaural summation and binaural release from masking. Keywords: Acceptable noise level; cochlear implant; hearing aid; bimodal hearing; profound hearing loss; binaural hearing